Grinding bur.



I. H. LETZ.

A RlNmNG BUR.

APPLICATION FILED IAN.I119I7 Y Patented Oct. 30,1917.

l Ilmmi UNITED sTAfrEs PATENT carica.

:roHN HOLLAND Lara, or cnowNroINr, INDIANA, AssIGNon 'ro Trng: Lnrz MANUFAC- TUBING COMPANY, or CROWN roINr, INDIANA', a CORPORATION or INDIANA.

GBINDING-zBUR.

Application nled January 17, 1917. 'Y Serial No.

To all 'whom it may concern.'

Be it known that I, JOHN HOLLAND Ln'rz, a citizen of the United States,and a resident of Crown Point, in the county of Lake and State of Indiana, have invented certain new and useful Improvements in Grinding- Burs, of which the following is a full, clear,

and exact specification. f

My invention is concerned with grinding burs of the type shown in the Letz Patent No. 437,699, and is designed to produce a dress of the bur that will' `grind more rapidly and economically than can be done with'the dress shown in the aforesaid patent.

To illustrate my invention, I have annexed hereto a single sheet of drawings, in

which the same reference characters are used to designate identical parts in all the figures, of which,-

Figure 1 is a view of the face of a complete bur containing my invention;

Fig. 2 is a section on the line 2- 2 of Fig. 1; and

Fig. 3 is an enlarged view of a portion of "Ihe body of the bur is made up preferably of a thin annular casting, which may be reinforced on its back by employing one or more annular ribs 1'. Its upper or grinding face is generally iat, except as it is broken by the grinding ribs to be described,

and which it will be understood are ordi-l narily cast integral with the body and ground oil' so as to form on all of them cutting edges and grinding surfaces in the same plane and adapted .to coperate with similar edges and surfaces simlarl formed on the similar ribs of the oppose the companion bur.

The ribs are preferably arranged in groups substantially triangular in their general outline, preferably six in number. The

ribs going to make up each of the groups are preferably the same, so that the desemption of one group will sulice for all.

Considering an imaginary radial line running through the center of each group (such as a central vertical line in Fig. l) as the base line for the purposes of description, the main ribs a, b, c, d, and e 1n a group are set substantially parallel to each other and at an angle of say sixty degrees to the radial base line, and are preferably interrupted or broken so that.l each rib4 is made upA of a plurality of sections, such as spe'mcaunn of Letters raient.

face of Patented 01st. 30., 191'?. 142,802.

l r Y f I l l aaaaa'zababibzvbaacacaozvcaaddszaeae and e2. Intersecting these main ribs are the baille ribs f, g, h, j, c, and l, also broken luto st'mns fa f2s gv ga g21 ,La ha h2, .7.a .7l/v lo, k', and Z, these baffle ribs being parallel to each other and substantially parallel to the base line.- These sections of the baille ribs are, asit will be noted, in groups between the main ribs, and together with the main ribs, or their sections, form a series of par` tially open sockets having converging sides, such for instance as f and b g and c, f and o', la and c2, and so on. 'Ihe main ribs a, b, C,v and d of any series begin at such a point relative to the main ribs aand a of the adjacent series as to form a triangular with the baiile and main ribs, respectively,

of the companion bur in a direct shearing action, while the centrifugal force of the rotating bur forces the rain always out` ward, .and the converging ribs forming pockets crowd the grain up from the at.

surfaces of the burs so that it will necessarily be brought intothe shearing plane formed by the iat surfaces of the ribs.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

1. A' grinding bur consisting of a generally flat diskhaving a series of grinding rlbs' projecting therefrom and having'their at top surfaces in the same plane and form-` ing shearing edges, said ribs consistin of plural series of parallel ribs separate by other similar series of parallel ribs interrupted at intervals and extending at acute angles to the first-mentioned series, sections of one series of ribs beinginterposed between pairs of the other series of ribs so as `to form plural series of acute angles with small openings at their outwardly directed apexes said series of angles extending in the general direction of the adjacent periphery, and each of said series of angles being separated from the adjacent series by a considerable plane space,

2. A grinding bur consistingof a generally iiat disk having a series of grinding ribs projecting therefrom and having their fiat top surfaces in the same piane and forming shearing edges, said ribs consisting of plural series of parallel ribs interrupted at intervals and separated by other similar series of arallel ribs likewise interrupted at intervals and extending at acute angles to the first-mentioned series, sections of one series of ribs being interposed between pairs yof lthe other series of ribs so as to ferm plural series ef iacute angles with small mesme openings at their outwardly directed apexes, said series of angles extending in the general 15 direction of the adjacent periphery, and each of said series of angles being separated from the adjacent series by a conslderable plane space.

In Witness whereof, I have hereunto set 20 my hand and aiiixed myY seal, this 16th day of December, A. D. 1916.

Witness:

JOHN HOWARD MGELROY. 

